In the packaging of granular bulk products, such as dry pet food, it has been found that if such products are packaged in a sealed plastic bag, the bags, when stacked on a pallet, tend to either burst or topple over. The air inside the package causes the bag to appear to be inflated, i.e., "balloon," as it is placed under increasing pressure. The ballooning is the result of pressurization within the bag, as the bag is flattened to a point at which the atmosphere sealed therewithin is placed under pressure. The result is that the pressure within the bags causes bags to burst, or causes the stack to topple, or both.
Typically, the bags contain relatively large amounts of packaged product, e.g., from 5 to 20 or more kilograms of granular product. It would be desirable to provide a means for packaging bulk granular product in plastic bags, with the packaged product being stackable without causing the bags to burst or topple over.